Buildings and other structures must be cooled and heated as simply and efficiently as possible. A past example of a cooling and heating system is shown in U.S. Pat. No. 3,636,721 to Rex (hereinafter the ""721 patent). The ""721 patent primarily discloses a control system for a thermal storage tank where excess heat is stored during occupied hours and used to heat the building during unoccupied hours without running the refrigeration machine, thus increasing efficiency of the system.
The ""721 control system is capable of cooling or heating any zone. All ventilation loads, exterior building transmission loads, interior people loads, equipment loads, and solar loads can be satisfied with this system. The ""721 disclosure calls for a four pipe system which employs a pair of chilled water mains piped to a cooling coil and a pair of hot water mains piped to a heating coil. Both coils are located within the fan coil unit and each zone (room or space) can thus be cooled or heated year round.
There are other systems used to cool or heat a building which employ a single pair of mains, wherein during the heating season (winter) hot water is piped to a single coil within the fan coil unit to heat the zone, and wherein during the cooling season (summer) chilled water is piped to the single coil within the fan coil unit to cool the zone. This is called a two pipe system.
This type of two pipe xe2x80x9cchangeover systemxe2x80x9d can deliver less than desirable results during the spring and fall of the year, because cool mornings require hot water in the mains and sunny afternoons require chilled water in the mains. Changeover can be thus be lengthy resulting in less than desirable conditions in the zones or spaces or rooms. Additionally, the cold North exposure side of the building may require heat while the sunny South exposure side of the building may, at the same time, require cooling. This necessitates sub-zoning of the building exposures with attendant zone valves and additional piping systems. This all results in a much more complex and expensive system.
There is a need for a better system which can readily heat or cool any zone regardless of the time of the year.
The present invention is for a variable constant volume cooling/heating unit and system. The system comprises a single chilled water supply pipe, a single hot water supply pipe, a single return pipe, and a control system on a single coil in a fan coil unit which can heat or cool any zone regardless of the time of the year, that is (regardless of the season).
A variable constant volume cooling/heating unit is provided. A hot and cold water is supplied to the unit to heat and cool the room or space. There is a two position three way valve, a warm water runout pipe for supplying warm water, a cold water runout pipe for supplying cold water, with the warm water runout pipe and cold water runout pipe connected to the two position three way valve. A modulating three way valve is provided such that that a supply pipe connects to the two position three way valve and modulating three way valve. The modulating three way valve is located downstream from the supply pipe. A pump is located downstream from the modulating three way valve, and a water coil having a coil outlet is located downstream from the pump, the pump for pumping water through the water coil. There is also a return water main and a return water runout pipe, the return water runout pipe connecting between the coil outlet and the return water main, the return water runout pipe connected to the coil outlet for receiving the flow of return water and connected to the return water main. A connecting pipe connects to the modulating three way valve and return water runout pipe and is for allowing return water to flow to the modulating three way valve and, wherein the modulating three way valve is for allowing all, a portion of, or none of the return water to flow there through.
A thermostat is provided for controlling the two position three way valve, modulating three position valve, pump, and a damper which controls the flow of incoming outside air.
The unit may be mounted above the ceiling of the room it is supplying There is also a ceiling return mounted to the room ceiling